Inox Cast Mini Injection Molding

Inox Cast is a division of SunOn Industrial Group and a Hong Kong Limited Liability Company with a diverse experience of more than 20 years. We supply products and services to customers around the world.

We specifically offer mini injection molding services for cable overmolding, seismic cable repair, low volume injection molding, low run production parts, ASTM test specimen, and more applications. At Inox Cast, rest assured that you can get the best services fitted for your applications.

Our mini injection molding can generate up to 12tons huge clamping force through mechanical advantage. It only uses minimal effort maintained by the injection cycle. For our mini injection molding, we use single hydraulic cylinder for carriage and clamping. Thus, minimizing the manufacturing cost.

Benefits of Inox Cast Mini Injection Molding

• Low quantity production runs
• Prototyping production parts
• Cable assembly overmolding
• Low cost injection molded parts
• Available in electric, hydraulic, or pneumatic models
• Competitive pricing

As a professional manufacturer and supplier, we serve various industries like medical injection molding, university school labs, electronic, automotive, and more. Here in Inox Cast, we are committed to making innovation and continuous improvements so we can exceed your expectations.

We supply wide range of mini injection molding services to different industries. For more than 20 years, Inox Cast has been recognized internationally because of our excellent quality products and unmatched services. For you business or project, you can surely trust Inox Cast to provide you mini injection molding services.

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Mini Injection Molding: The Ultimate Guide

This guide has all information you are looking for about mini injection molding.

So, if you want to be an expert in mini injection molding, read this guide.

1.  What Is Mini Injection Molding?

Mini injection molding is a manufacturing process for producing different parts in reasonable volume.

Ordinarily, unlike the normal injection molding used in mass-production processes, mini injection molding creates a few similar parts in succession.

In the recent past, this manufacturing process is becoming popular since it somewhat reduces cost per unit of the parts.

mini injection molding machine

Moreover, this process offers high repeatability and ideal design flexibility, allowing you to produce the particular volume of parts you need.

You can use this method to create plastic parts of various sizes and complexity, making it ideal for a wide range of applications.

2.  Mini Injection Molding Process

It is a relatively detailed and involving process that requires in-depth understanding and right equipment to execute.

Essentially, basic understanding enables you to establish features to consider when designing parts for this process and forecasting production schedules.

Nevertheless, the process starts with determining the design of CAD model. It merely revolves around choosing the color, texture and resin.

The next step is design verification with 3D printed, CNC machined and urethane cast prototypes.

It allows you to test whether plastic part meets the requirements for strength, function, durability and aesthetics.

What follows is DFM analysis, which aims to understand all potential risks or issues by updating CAD design to prevent future tooling modifications.

It is a critical phase in mini injection molding process since part modifications here take a few minutes and several days after tooling is complete.

The next stage is reviewing tooling design for approval. Here, you need to address all concerns and ensure you are satisfied with the design.

Steel cutting is the next stage, and it involves CNC machining, EDM and wire cutting to make core, cavity, filters and inserts.

mini injection molding process

What follows is samples’ first trial happening once fitting is done to resolve as many issues as possible before sending them out to the customer.

Second and third samples’ trials also take place depending on the complexity of tooling design requirements.

Once samples are approved, the production process kicks off, and the respective volume required is manufactured.

3.  Mold Considerations For Mini Injection Molding

Technically, molds are highly customizable and thus can create complex geometries with incredibly tight tolerances.

Hence, the main factors to consider when designing a mold for mini injection molding include the following;

• Cost of mold
• Resin
• Production throughput
• Component quality
• Parts’ geometric complexity
• Cavitation

Ideally, mold material influences length of molding process, mold longevity and actual cost.

Aluminum is seemingly more affordable and allows the plastic to cool faster for an overall more rapid production cycle.

On the other hand, steel molds are a bit costly but relatively durable, thus suitable for more aggressive resins.

However, you can use aluminum and steel to create complex molds.

Of course, production of most molds is through EDM or CNC milling; thus, they can be simple or complex depending on design demands.

4.  Machine Considerations For Mini Injection Molding

When choosing the right mini injection molding machine, you need to factor in some fundamental elements such as the following;

• Shot size

Select a mini injection molding machine that can insert the right amount of plastic or shot size into each mold.

This aspect is influenced by cushion and back pressure.

• Tonnage

It refers to the clamping force or pressures the machine can generate.

Ideally, different parts possess varying tonnage demands to maintain part integrity and keep the mold closed.

Hence, ensure you have the right amount of pressure to guarantee desired results.

• Shrinkage

Plastic shrinks as it cools, and properly designed molds account for such shrinkage to ensure the final product has right dimensions.

Different resins have varied amounts and rates of shrinkage; thus, material selection for the final part is vital during design phase.

5.  Choosing Material For Mini Injection Molding

Selecting the most suitable material for mini injection molding saves resources and ensures optimal product efficiency and manufacturability.

Thus, it is always fundamental to research the particular material appropriately to determine the ideal choice.

The main factors to look into when selecting the right one include the following;

Cost – Figure out the price of specific material you are selecting and establish whether it guarantees the return on investment.

Weight – Lightweight materials are preferable as far as mini injection molding is concerned. Such materials make it easy to create both complex and simple designs.

Durability – Determine the overall tensile strength of the material and its resistance to numerous environmental factors. It helps in establishing the longevity of the final part product.

Flexibility – It is advisable to determine how versatile the specific material you select is. It makes it easier to create a wide range of complex parts and reduces tooling costs.

Unique properties – Ideally, check all the special attributes of the material such as temperature resistance, dimensional stability, weatherability, machinability and impact resistance etc.

6.  Advantages Of Mini Injection Molding

Irrespective of the material you are using for mini injection molding based on your product demands, this process offers several advantages such as follows;

Scaling down production en masse – Once you determine the initial costs per unit, this manufacturing process becomes exceptionally cost-effective.

Fast turnaround – The process is fast, incredibly efficient and well-suited for small and medium scale applications.

Minimal waste – Mini injection molding features properly designed molds and processing, enabling it to produce little waste, if any.

Besides, any waste produced can be grinded, melted and used again.

Customization – Mechanical features of resins in mini injection molding can easily be engineered to meet particular design requirements by using coolants, additives and fillers.

Easily automated – Depending on the machine you are using, you can fully automate the mini injection molding process, further reducing parts’ cost.

Allows repetition and consistency – This process leverages repetition and consistency; thus, you can produce a second part identical to the first one.

7.  Main Applications For Mini Injection Molded Parts

Mini injection molding process is often used in producing parts for different applications across various sectors.

However, the common applications include the following;

• Automotive OEM parts
• Consumer electronics
• Industrial components
• Building and construction
• Packaging and beverage bottling
• Medical devices
• Parts ideal for high-wear environments

8.  Role Of Auxiliary Equipment In Mini Injection Molding

Ideally, most mini injection molding machines make high-quality part production.

However, they rely on auxiliary equipment surrounding them to fulfil the entire process effectively.

Auxiliary equipment in this manufacturing process are essential in different ways, including the following;

• Drying and preparing all the raw materials accordingly with minimal waste
• Delivering materials to mini injection molding machines without necessarily contaminating or moisture regain.
• Maintaining consistency of the process over long production runs
• Effective management and reuse of scrap material
• Assuring precise and reliable temperature control for energy efficiency and product quality.
• Removal and handling of finished parts accordingly

In mini injection molding, auxiliary equipment used for material, ingredient and batch storage include; surge bins, hoppers and silos.

Material conveying process is facilitated by pumps, conveying controls, material selection tables, mobile conveying systems, vacuum conveying systems, conveying lines etc.

Drying, pre-heating or dehumidifying material is done by drying systems, dehumidification systems, machine sides and mini-systems.

Material weighing, ingredient dispensing, and batch blending are facilitated by feeders, blenders, mixers and weighing scales.

Process equipment cooling is offered by central chillers, recirculating water systems and adiabatic cooling towers.

Granulation systems, on the other hand, facilitate scrap material reprocessing.

In a nutshell, mini injection molding is easily attainable with the help of multiple auxiliary equipment before, during and after the manufacturing process.

9.  Common Defects In Mini Injection Molding

Most defects in mini injection molding are connected to melted material flow or non-uniform cooling rate during solidification.

The main defects to always keep in mind include the following;

Warping – It happens when certain sections cool faster than others leading to bending on the part due to internal stresses.

Often, parts with uneven wall thickness are prone to this defect.

Sink marks – Usually occurs when due to solidification of interior parts before its surface, causing a small recess on a flat surface.

Thick-walled or poorly designed parts are usually prone to sinking.

Drag marks – These arise from part walls sliding and scraping against mold during ejection since it applies pressure on the mold.

Most parts prone to drag marks are those with vertical walls.

Knit lines – Small hair-like discolorations often develop when two flows meet, causing knit lines. These lines affect parts’ aesthetics and reduce overall strength.

Short shots – It usually arises due to trapped air in the mold inhibiting material flow during injection hence an incomplete part.

Thin-walled parts are often predisposed to this defect.

10.  Cost Reduction Tips In Mini Injection Molding

The underlining essence of using mini injection molding instead of the traditional injection molding process is to reduce cost and wastage significantly.

Ordinarily, the biggest cost drivers in mini injection molding include tooling, material and production.

Here are the vital tips to help in reducing costs in this manufacturing process;

Stick to straight-pull mold – In-mold mechanisms and side-action cores tend to inflate tooling costs by up to 30%.

Thus, to keep production on a budget, it would be ideal to avoid using in-mold mechanisms and side-action cores unless where necessary.

Redesigning parts to avoid undercuts – Typically, undercuts inflate cost, complexity and maintenance of the mold.

Thus, a creative redesign would eliminate unnecessary undercuts.

Create smaller injection molded parts – It is easier to mold smaller parts faster, leading to higher production volume and lowering cost per part.

Avoid small details – Usually, small details need longer machining and finishing times and avoiding them would enable you to cut costs significantly.

Reduce wall thickness – To obtain a smaller part volume, it is necessary to reduce wall thickness. It implies use of less material and an accelerated mini injection molding process.

Consider secondary processes – Mini injection molding for low volume parts may be cost-effective to use secondary operations to complete.

11.  Steps In Mini Injection Molding

In layman’s understanding, mini injection molding involves the following steps;

• Material is dried and placed in a hopper to mix with the selected coloring pigment and any other reinforcing additives.
• Granules are fed in a barrel for simultaneous heating, mixing and moving towards mold by a variable pitch screw.

Here, screw and barrel geometry are optimized to facilitate a pressure build-up to the right levels and melt material.

• Melted material is injected into mold via a runner system where it fills the entire cavity. As the molten material cools, it re-solidifies and takes the mold shape.
• Mold opens, and solid part is pushed out by ejector pins. Mold closes, and process repeats.

You can repeat the entire process rapidly since the cycle takes about 30-90 seconds, depending on the part size.

Once part is ejected, it is dispensed on a conveyor belt and ready to use right away with little or no post-processing operations.

mini injection molding process

12.  Factors Determining Cost Of Mini Injection Molding

Many factors go into determining the actual cost of a typical mini injection molding process.

For instance, the type of material used is a vital consideration when figuring out the full cost of this process.

Some materials are cheaper, whereas others tend to be costly depending on size, thickness and other unique properties.

The design construction of the part you are molding using this process is another determinant cost factor.

Often, customized parts are a bit expensive to produce because they involve several small details, unlike standard parts.

Also, the specific surface finishing and post-molding operations you need for your part influence the full cost of the process.

Some parts hardly require such operations; thus, you can use them right away from injection molding, and this reduces cost.

On the other hand, others, due to performance and aesthetics, require such post-molding procedures, which increase the overall cost.

In essence, there is no fixed cost for mini injection molding. It depends on several factors.

13.  Effects Of Uniform Wall Thickness In Mini Injection Molding

It is important to consider wall thickness when designing parts for mini injection molding.

This element influences several core part characteristics such as cost, mechanical performance and aesthetics.

Besides, thorough consideration of uniform wall thickness relieves you from costly delays in your schedule arising from molding issues and mold modifications.

Notably, you should determine nominal wall thickness by functional performance requirements.

Moreover, acceptable stress and anticipated part longevity should help establish nominal wall thickness.

Extremely thin walls may require excessive pressure or cause air traps if the material does not fill completely.

On the other hand, thicker walls tend to be more expensive because of greater material usage and longer machine cycle times.

Related Resource:

3D Injection Molding

Small Scale Injection Molding

High Volume Injection Molding

Short Run Injection Molding

Large Injection Molding

For inquiry or questions on mini injection molding, contact us now.